1. Field of Invention
This invention relates generally to microscope lens cover assemblies, and more specifically to objective lens cover assemblies employed in conjunction with disposable sterile and nonsterile operating microscope drapes.
2. Description of the Prior Art
Operating microscopes are employed in the performance of various surgical procedures. During the performance of such procedures it is necessary to maintain the microscope and surgical field in sterile condition. Difficulty in maintaining sterility is presented by the need to position the microscope objective lens in close proximity to the surgical site. During the performance of surgical procedures the objective lens can become smeared with matter from or near the surgical site. In particular, the lens may become splattered with blood, bone fragments or other solutions introduced into the operating site. Additionally, surgical instruments may contact the objective lens surface scratching or damaging the lens.
Prior art devices have generally provided sterile drape assemblies fabricated of a plastic material to completely house the microscope and microscope support structures. These devices include objective lens cover assemblies of various configurations. However, none of these prior art lens cover assemblies have proved to be entirely satisfactory.
U.S. Pat. No. 3,528,720 to Treace discloses a clear plastic envelope enclosure adapted to be removably fitted over a cantilever supported operating microscope. The drape includes a circular aperture positioned to receive the objective lens of the operating microscope, and an objective lens ring adapted to frictionally engage the objective lens frame. The ring is fabricated of a slightly resilient deformable plastic material. Structurally, the ring includes an annular body frusto-conical in form for engaging the objective lens frame. The upper circumferential portion of the annular body is provided with an external flange for securing the ring to the drape. The lower circumferential portion of the annular body is provided with a circumferential inwardly directed flange which serves as a guard means for protecting the objective lens. Treace does not disclose a means for enclosing the objective lens of the microscope. The bottom of the annular body of the Treace device is open. Fundamentally, the Treace device provides a guard means for protecting the objective lens from damage by hand held surgical instruments (col. 4, lines 64-71). The open lens ring presents the danger that the microscope objective lens will render the surgical field unsterile. Additionally, difficulties arise when matter from the surgical field smears the objective lens.
U.S. Pat. No. 3,698,791 to Walchle et al. discloses a sterile operating microscope drape including an integral lens panel secured in an associated lens housing. The lens housing frictionally receives the objective lens through an aperture in the drape. The lens cover and housing cannot be disassociated from the drape. In cases in which it is necessary to remove the lens cover, the entire drape must be removed.
U.S. Pat. No. 3,796,477, to Geracci discloses a lens ring housing and cover assembly including a resilient lens housing adapted to frictionally receive the objective lens and lens ring of an operating microscope, and a removable lens cover. The lens housing includes an inner circumferential groove for receiving the outer peripheral portions of the lens cover, an annular glare shield, and a recess extending outwardly from the inner to the outer walls of the housing. The lens cover includes an outwardly extending manipulative handle which is received in the recess for disassociating the lens cover from the housing by pulling downwardly on the lens handle. Geracci does not provide a structure which readily facilitates the substitution of replacement lens covers during the progress of operative procedures should the same become necessary.